1. Technical Field
The present invention relates to a liquid crystal display device and particularly relates to a technique of collecting outside light.
2. Related Art
A conventional liquid crystal display device guides light emitted from a backlight module using a light guide plate to backside of a liquid crystal panel, and diffuses the light evenly using a diffuser, thereby making the light incident on the liquid crystal panel as a surface light source. A CCFL tube or an LED is used as a backlight. Accordingly, a viewer can recognize a liquid crystal display with adequate brightness.
There is a type of liquid crystal display device that collects outside light as a part of the backlight, so as to reduce the power consumption of the backlight module. For example, the liquid crystal display device disclosed in Patent Document No. 1 guides outside light reflected at the reflector to inside of the liquid crystal display device via a semi-transmissive reflector. In this way, the device uses both of the collected outside light and the light from the backlight module.
Another type of liquid crystal display device is a transparent liquid crystal display device. The transparent liquid crystal display device is a liquid crystal display device that is not equipped with any backlight module. The transparent liquid crystal display device displays an image displayed on the liquid crystal panel, by overlapping it on a background, and so does not include either a light guide plate or a diffuser. An example of the transparent liquid crystal display device is a head-up display.
Patent Document 1: Japanese Patent Application Publication No. 2000-356772
However, the liquid crystal display device described in Patent Document No. 1 collects light from the reflector, and therefore only the light irradiated from above the liquid crystal display device can be guided. This prevents the outside light from being made use of to the full extent, and makes it impossible to obtain sufficient brightness. In addition, the transparent liquid crystal display device is a display device which displays a liquid crystal display image by overlapping it onto the background, and cannot display only the liquid crystal display image.
The present invention has been conceived of in view of such circumstances, and has an object of providing a liquid crystal display device which can efficiently use the outside light.